Audio systems, devices, mems microphones, and methods thereof

ABSTRACT

In one embodiment, a MEMS microphone can be coupled to an acoustic horn to provide various benefits and improvements including, but not limited to, at-a-distance acoustic signal reception with improvements in signal-to-noise ratio and directional preference.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application claims priority to U.S. Provisional Application No.62/805,866 filed on Feb. 14, 2019, the content of which is herebyincorporated by reference.

BACKGROUND

The present invention relates, in general, to electronics, and moreparticularly to audio systems, hearing aids, over-the-counter hearingaids, hearables, wearables, personal sound amplifiers, acousticsurveillance tools, built-in microphone systems, MEMS microphones, cellphones, tablets, computers, televisions, vehicle infotainment systems,smart speakers and devices, voice controlled systems, audio devices,and/or methods.

Sound pressure levels can be measured in units called decibels(abbreviated as dB). Sound levels diminish as the distance between asound source and the sound receiver increases. For example,conversational speech measured as 65 dB at 50 centimeters away from aspeaker can measure at 45 dB when measured from 500 centimeters away.Human speech is typically comprised of voiced and unvoiced sounds thatare produced at a wide variety of frequencies. A large portion of humanspeech information is transmitted at frequencies above 1500 Hz.

A microphone is a transducer that converts sound into an electricalsignal. Microphone self-noise (or equivalent noise level) is anelectrical signal which a microphone produces of itself. Microphoneself-noise can occur even when no sound source is present. Microphoneself-noise can be a problem in many audio systems. Increased microphoneself-noise decreases the signal-to-noise ratio (SNR) of a microphone.The noise generated by microphone self-noise can be distracting to usersof audio systems and can make it difficult for users of an audio systemto understand the intended signal. In order to increase SNR, arelatively noisy mic can be placed closer to the source to increase thesignal strength. Generally, microphones that are rated with lowerself-noise and higher SNR are expensive, large diaphragm, condenser-typemicrophones.

MEMS (MicroElectroMechanical Systems) microphones are variants of thecondenser microphone design. A pressure-sensitive diaphragm can beetched directly into a silicon wafer by MEMS processing techniques. MEMSmicrophones can be very small and low cost. The port opening of apackage containing a MEMS microphone can be a mere 0.2 millimeters (mm).The die size of a MEMS microphone may be even smaller. Conventional MEMSmicrophones, however, suffer from high self-noise figures as aconsequence of their small size. Conventional MEMS microphones are alsoomni-directional, meaning that they show no preference for incomingsignal direction. In order to achieve directional preference with a MEMSmicrophone system, conventional MEMS microphone systems use an array ofMEMS microphones and signal processing techniques.

A small and low cost microphone is desirable for many audio systems,including for example, audio system applications requiring directionalpreference and at-a-distance acoustic signal reception.

Accordingly, it is desirable to have a MEMS microphone or microphonesystem that exhibits, among other things, high SNR and directionalpreference without requiring an array of microphones and increasedsignal processing. Additionally, it is beneficial for such a system tobe physically configured to achieve high manufacturability, compactdimensions for small applications, and reduced cost while maintainingand improving efficacy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of an acoustic horn for MEMSmicrophones, audio systems and/or devices in accordance with variousembodiments;

FIG. 2 illustrates a schematic diagram of an acoustic horn for MEMSmicrophones, audio systems and/or devices in accordance with variousembodiments;

FIG. 3 illustrates a schematic diagram of an acoustic horn for MEMSmicrophones, audio systems and/or devices in accordance with variousembodiments;

FIG. 4 illustrates a schematic diagram of an acoustic horn for MEMSmicrophone, audio system and/or device in accordance with variousembodiments;

FIG. 5 illustrates a schematic diagram of an acoustic horn for MEMSmicrophones, audio systems and/or devices in accordance with variousembodiments;

FIG. 6 illustrates a schematic diagram of an acoustic horn for MEMSmicrophones, audio systems and/or devices in accordance with variousembodiments;

FIG. 7 illustrates a schematic diagram of an acoustic horn for MEMSmicrophones, audio systems, and/or devices in accordance with variousembodiments;

FIG. 8 illustrates a schematic diagram of an acoustic horn for MEMSmicrophones, audio systems, and/or devices in accordance with variousembodiments;

FIG. 9 illustrates a schematic diagram of a miniature acoustic horn forMEMS microphones, audio systems, and/or devices in accordance withvarious embodiments.

The drawings and detailed description are provided in order to enable aperson skilled in the applicable arts to make and use the invention. Thesystems, structures, circuits, devices, elements, schematics, signals,signal processing schemes, flow charts, diagrams, algorithms, frequencyvalues and ranges, amplitude values and ranges, methods, source code,examples, etc., and the written descriptions are illustrative and notintended to be limiting of the disclosure. Descriptions and details ofwell-known steps and elements are omitted for simplicity of thedescription.

For simplicity and clarity of the illustration, elements in the figuresare not necessarily drawn to scale, and the same reference numbers indifferent figures denote the same elements.

As used herein, the term and/or includes any and all combinations of oneor more of the associated listed items. In addition, the terminologyused herein is for the purpose of describing particular embodiments onlyand is not intended to be limiting of the disclosure. As used herein,the singular forms are intended to include the plural forms as well,unless the context clearly indicates otherwise. It will be furtherunderstood that the terms comprise, comprises, comprising, include,includes, and/or including, when used in this specification and claims,are intended to specify a non-exclusive inclusion of stated features,numbers, steps, acts, operations, values, elements, and/or components,but do not preclude the presence or addition of one or more otherfeatures, numbers, steps, acts, operations, values, elements,components, and/or groups thereof. It will be understood that, althoughthe terms first, second, etc. may be used herein to describe varioussignals, portions of signals, ranges, members, and/or elements, thesesignals, portions of signals, ranges, members, and/or elements shouldnot be limited by these terms. These terms are only used to distinguishone signal, portion of a signal, range, member, and/or element fromanother. Thus, for example, a first signal, a first portion of a signal,a first range, a first member, and/or a first element discussed belowcould be termed a second signal, a second portion of a signal, a secondrange, a second member, and/or a second element without departing fromthe teachings of the present disclosure. It will be appreciated by thoseskilled in the art that words, during, while, concurrently, and when asused herein related to audio systems, devices, methods, signalprocessing and so forth, are not limited to a meaning that an action,step, function, or process must take place instantly upon an initiatingaction, step, process, or function, but can be understood to includesome small but reasonable delay, such as propagation delay, between thereaction that is initiated by the initial action, step, process, orfunction. Additionally, the terms during, while, concurrently, and whenare not limited to a meaning that an action, step, function, or processonly occur during the duration of another action, step, function, orprocess, but can be understood to mean a certain action, step, function,or process occurs at least within some portion of a duration of anotheraction, step, function, or process or at least within some portion of aduration of an initiating action, step, function, or process or within asmall but reasonable delay after an initiating action, step, function,or process. Furthermore, as used herein, the term range, may be used todescribe a set of frequencies having an approximate upper andapproximate lower bound, however, the term range may also indicate a setof frequencies having an approximate lower bound and no defined upperbound, or an upper bound which is defined by some other characteristicof the system. The term range may also indicate a set of frequencieshaving an approximate upper bound and no defined lower bound, or a lowerbound which is defined by some other characteristic of the system.Reference to “one embodiment” or “an embodiment” means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the presentdisclosure. Thus, appearances of the phrases “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily all referring to the same embodiment, but in some cases itmay. The use of words about, approximately or substantially means avalue of an element is expected to be close to a stated value orposition. However, as is well known in the art there are always minorvariances preventing values or positions from being exactly stated. Itis further understood that the embodiments illustrated and describedhereinafter suitably may have embodiments and/or may be practiced in theabsence of any element that is not specifically disclosed herein.Furthermore, it is understood that in some cases the embodimentsillustrated and described hereinafter suitably may have embodimentsand/or may be practiced with one or more of the illustrated or describedelements, blocks, or signal processing steps omitted.

Those skilled in the art will understand that as used herein, the termaudible frequencies can refer to a range of frequencies associated withthe range of frequencies generally audible to humans, for example, fromabout 20 Hertz (“Hz”) to about 20,000 Hz. In addition, as used herein,audible frequencies can also refer to any frequency or frequency rangewhere the invention described herein may find application.

Those skilled in the art will understand that as used herein, the termeffective length can refer to a linear length, a coiled length, anunfolded length, an unbent length, an acoustic length, or a length thatwill be equal to or will be qualitatively consistent with acorresponding physical length for air-conduction sound propagation.

Those skilled in the art will understand that as used herein, the termsaudio device or audio system may, can refer to a stand-alone system or asubsystem of a larger system. A non-limiting list of example audiosystems can include: hearing aids, over-the-counter hearing aids,hearables, wearables, personal sound amplifiers, televisions, radios,cell phones, telephones, computers, laptops, tablets, vehicleinfotainment systems, audio processing equipment and devices, personalmedia players, portable media players, audio reception systems,receivers, public address systems, media delivery systems, internetmedia players, smart speakers and devices, voice controlled systems,voice activated systems, recording devices, acoustic surveillance tools,built-in microphone systems, MEMS microphones, audio devices, subsystemswithin any of the above devices or systems, or any other device orsystem which processes audio signals.

Multiple instances of embodiments described or illustrated herein may beused within a single audio device or system. As an example, multipleinstances of embodiments described or illustrated herein may enable theuse of multiple MEMS microphones. As another example, multiple instancesof embodiments described or illustrated herein may enable a stereo audiodevice comprising a first instance of an embodiment for a right MEMSmicrophone and a second instance of an embodiment for a left MEMSmicrophone.

The inventor is fully informed of the standards and application of thespecial provisions of 35 U.S.C. § 112(f). Thus, the use of the words“function,” “means” or “step” in the Detailed Description of theInvention or claims is not intended to somehow indicate a desire toinvoke the special provisions of 35 U.S.C. § 112(f), to define theinvention. To the contrary, if the provisions of 35 U.S.C. § 112(f) aresought to be invoked to define the inventions, the claims willspecifically and expressly state the exact phrases “means for” or “stepfor” and the specific function (e.g., “means for filtering”), withoutalso reciting in such phrases any structure, material or act in supportof the function. Thus, even when the claims recite a “means for . . . ”or “step for . . . ” if the claims also recite any structure, material,or acts in support of that means or step, or that perform the recitedfunction, then it is the clear intention of the inventor not to invokethe provisions of 35 U.S.C. § 112(f). Moreover, even if the provisionsof 35 U.S.C. § 112(f) are invoked to define the claimed inventions, itis intended that the inventions not be limited only to the specificstructure, material or acts that are described in the illustratedembodiments, but in addition, include any and all structures, materials,or acts that perform the claimed function as described in alternativeembodiments or forms of the invention, or that are well known present orlater-developed, equivalent structures, material, or acts for performingthe claimed function.

In the following description, and for the purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the various aspects of the invention. It will beunderstood, however, by those skilled in the relevant arts, that thepresent invention may be practiced without these specific details. Inother instances, known structures and devices are shown or discussedmore generally in order to avoid obscuring the invention. In many cases,a description of the operation is sufficient to enable one to implementthe various forms of the invention, particularly when the operation isto be implemented in software, hardware or a combination of both. Itshould be noted that there are many different and alternativeconfigurations, devices, and technologies to which the disclosedinventions may be applied. Thus, the full scope of the invention is notlimited to the examples that are described below.

Various representative implementations of the present invention may beapplied to any system for audio devices. For example, certainrepresentative implementations may include: hearing aid devices,personal sound amplification products, acoustic surveillance tools,built-in microphone systems, audio systems, devices, and methods.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of an audio system 100. Audiosystem 100 can comprise a MEMS microphone 110 and an acoustic horn 120which can be coupled directly or indirectly (e.g. via an intermediatestructure, material, or attachment mechanism) to MEMS microphone 110.MEMS microphone 110 may be any type of MEMS microphone, for example,MEMS microphone 110 may be a MEMS microphone die, a substrate of a MEMSmicrophone, a circuit board to which a MEMS microphone is mounted, a topport MEMS microphone, a bottom port MEMS microphone, a side port MEMSmicrophone, a MEMS microphone with digital output, or a MEMS microphonewith analog output. Acoustic horn 120 may be any type of acoustic horn,for example, acoustic horn 120 can be an exponential horn, a parabolichorn, a conical horn, a hyperbolic horn, a hyperbolic-exponential orhypex horn, a tractrix horn, a flaring horn, a horn with a smoothcontinuous surface, or a horn with a discontinuous or stepped surface.Acoustic horn 120 can be made from any type of material suitable for anacoustic horn, including for example, plastics, polymers, metals,alloys, ceramics, materials facilitating acoustic amplification,materials facilitating acoustic attenuation, and mixtures orcombinations thereof, etc.

Acoustic horn 120 can act as an acoustic transformer, changing lowpressure and high volume at the mouth 140 of horn 120 to high pressureand low volume at the throat 130 of horn 120. The cross-sectional area150 of horn 120 can be designed to increase from throat 130 along theaxis 160 toward mouth 140. The cross-sectional area 150 of horn 120 maybe of any shape, for example, cross-sectional area 150 may be circular,oval, rectangular, square, multi-sided, or combinations of these. For anexponential horn, cross-sectional area 150 (A_(x)) of the horn 120 ateach location along axis 160 can equal the cross-sectional area at thethroat 130 (A_(t)) of the horn times Euler's number (e=2.71818 . . . )raised to the power of the quantity: 4 times pi times ‘x’ divided by thewavelength (λ) of the cutoff frequency of the horn, where x representsthe variable length at each location along axis 160 as measured fromthroat 130; according to the equation:

A_(x)=A_(t)e^(4πx/λ)

According to an embodiment, the diameter of throat 130 can be about 1millimeter (mm) and the cutoff frequency of horn 120 can be designed toequal about 1000 Hz. The acoustic wavelength of a 1000 Hz signal can beabout 34 centimeters (cm). To act as an acoustic transformer, theeffective length of the horn from throat 130 to mouth 140 can be atleast ¼ of the wavelength at the cutoff frequency or about 8.5 cmaccording to an embodiment. This can result in a diameter of mouth 140of about 4.8 mm. Efficient amplification for this embodiment can beginat least ½ octaves above the cutoff frequency or about 1500 Hz, where alarge portion of speech information exists. The configuration of horn120, creates an amplified signal prior to the acoustic signal receptionby MEMS microphone 110. This results in an improved signal-to-noiseratio. The acoustic horn 120 can also provide directional preference forthe MEMS microphone 110. As shown, the size of acoustic horn 120 can bedetermined by the specified cutoff frequency and the diameter of throat130. Accordingly, the embodiments described herein can exploit the smallport characteristics of the MEMS microphone and high frequency contentof intelligible human speech to great advantages. The embodimentsdescribed herein and their associated advantages and benefits, uniquelyapplied to audio systems designed for improving human speechintelligibility, have not heretofore been recognized by any prior artusages of MEMS microphones despite the long existence and understandingof horns to those of ordinary skill in the relevant arts.

According to another embodiment, audio system 100 can have an acoustichorn 120 which can form an integrated feature of MEMS microphone 110.

According to an embodiment, acoustic horn 120 can be integral with thesubstrate or housing, or casing of MEMS microphone 110. For example,acoustic horn 120 can be integral with the casing or packaging of MEMSmicrophone 110. According to another example, acoustic horn 120 can beintegrated with the material surrounding the port of MEMS microphone110.

Acoustic horn 120 may be constructed from a multitude of differentmaterials, for example, acoustic horn 120 may be constructed with 3-Dprinted materials, injection molded plastics, silicone, cast materials,metal, ceramics, natural materials, rubber, materials facilitatingacoustic amplification, materials facilitating acoustic attenuation, orcombinations of materials. Furthermore, acoustic horn 120 may be curved,spiraled, angled, folded, bent, or otherwise non-linearly arranged inorder to allow the horn to fit certain physical dimensions orapplications while still maintaining the desired amplification, SNR, anddirectionality requirements of the horn.

Still referring to FIG. 1, acoustic horn 120 can be designed to provideamplification for frequencies above 2000 Hz in order to achieve benefitsassociated with improving human speech intelligibility in audio systems.The air conduction wavelength for a cutoff frequency of 2000 Hz is about16.57 cm for standard conditions for temperature and pressure.Accordingly, for a horn with a cutoff frequency of about 2000 Hz, aminimum effective length for acoustic horn 120 can be about 4.14 cm(=16.57 cm/4) or 41.4 mm. One skilled in the art will recognize that theeffective length of acoustic horn 120 may be shorter or longer than 41.4mm. For example, a horn can be designed to provide amplification forvarious frequencies associated with various components of human speech.According to one embodiment, an acoustic horn can have an effectivelength within the range of 40 mm to 250 mm.

Again, referring to FIG. 1, acoustic horn 120 can be designed to providespecific values of amplification in order to achieve benefits associatedwith improving human speech intelligibility in audio systems includingthe improvement of SNR of a MEMS microphone. The value of amplificationof acoustic horn 120 is a function of the ratio of the cross-sectionalarea of mouth 140 to the cross-sectional area of throat 130. Forexample, according to an embodiment, the ratio of the cross-sectionalarea of mouth 140 to the cross-sectional area of throat 130 can be 4:1.According to another embodiment, the ratio of the cross-sectional areaof mouth 140 to the cross-sectional area of throat 130 can be between4:1 and 25:1 in order to provide benefits associated with improvinghuman speech intelligibility in audio systems including the improvementof SNR of a MEMS microphone.

FIG. 2 illustrates a schematic diagram of an audio system 200 comprisinga MEMS microphone 210 with acoustic horn 220. MEMS microphone 210 can becoupled to acoustic horn 220 directly or indirectly via an intermediatecomponent or components (not shown). Intermediate component(s) caninclude, a gasket, a diaphragm, a moisture barrier, a flexible tube, athrough-hole mounting on a circuit board, mounting screws, an attachmentmechanism, an intermediate structure, a buffer material, a sealant, atape, a film, a layer, an adhesive, glue, or epoxy, etc. MEMS microphone210 may be any type of MEMS microphone, for example, MEMS microphone 210may be a MEMS microphone die, a substrate of a MEMS microphone, acircuit board to which a MEMS microphone is mounted, a top port MEMSmicrophone, a bottom port MEMS microphone, a side port MEMS microphone,a MEMS microphone with digital output, or a MEMS microphone with analogoutput. Acoustic horn 220 may be any type of acoustic horn, for example,acoustic horn 220 may be an exponential horn, a parabolic horn, aconical horn, a hyperbolic horn, a hyperbolic-exponential or hypex horn,a tractrix horn, a flaring horn, a horn with a smooth continuoussurface, or a horn with discontinuous or stepped surface. Acoustic horn220 can act as an acoustic transformer, changing low pressure and highvolume at the mouth 240 of the horn to high pressure and low volume atthe throat 230 of the horn. The cross-sectional area of the horn ateffective length 250 from the throat 230 can be designed to increase asdistance 260 from the throat 230 increases. The cross-sectional area 250of horn 220 at an effective length along axis 260 from throat 230 may beof any shape, for example, the cross-sectional area may be circular,oval, rectangular, square, multi-sided, or combinations of these.

According to an embodiment, audio system 200 can comprise a MEMSmicrophone 210 with acoustic horn 220 wherein acoustic horn 220 and MEMSmicrophone 210 are distinct components joined, attached, or coupledtogether.

According to another embodiment, audio system 200 can comprise a MEMSmicrophone 210 with acoustic horn 220 wherein acoustic horn 220 can beintegrated with a part of another structure, for example, a molding, acasing, a surface feature, a printed circuit board, steering wheel, cellphone case, parabolic sound collecting dish, television case, monitorcase, tablet case, cell phone case, hearable case, hearing aid housing,or laptop case, or a secondary case intended to be attached overlying atleast a portion of a an audio system, television, monitor, tablet, cellphone, hearable, or laptop.

FIG. 3 illustrates a schematic diagram of an audio system 300 similar toaudio system 200 of FIG. 2 and/or audio system 100 of FIG. 1,additionally comprising an interface component 370 which can provide anattachment, interface, or coupling between a MEMS microphone 310 and anacoustic horn 320. Interface component 370 can be any type of interfacecomponent or components, for example, interface component 370 can be agasket, a diaphragm, a moisture barrier, a flexible tube, a through-holemounting on a circuit board, mounting screws, an attachment mechanism,an intermediate structure, a buffer material, a tape, a film, a layer, asealant, an adhesive, glue, or epoxy, etc.

According to an embodiment, interface component 370 can further comprisean opening, a feature, a medium, sound transmitting material, or a holethat can allow sound energy to pass from acoustic horn 320 to MEMSmicrophone 310.

FIG. 4 illustrates a schematic diagram of an audio system 400 similar toany of audio system 300 of FIG. 3, audio system 200 of FIG. 2, and/oraudio system 100 of FIG. 1, additionally comprising a bend or angle 480within acoustic horn 420. Bend 480 can be designed so that acoustic horn420 continues to act as an acoustic transformer, changing low pressureand high volume at the mouth 440 of the horn 420 to high pressure andlow volume at the throat 430 of the horn 420. Multiple bends such asbend 480 may be employed to “fold” acoustic horn 420 into a compactedspace while retaining the pre-amplifier and directional preferenceproperties of acoustic horn 420. Bend 480 can assume any configuration,for example, bend(s) 480 may be a conic helix, a conic spiral, alogarithmic spiral, a seashell surface, a labyrinth, a folded structure,or sound amplifying structure.

FIG. 5 illustrates an audio system 500 implementing a MEMS microphonewith acoustic horn 520. According to an embodiment, audio device 500 canbe a behind-the-ear (BTE) hearing aid. According to other embodiments,audio device 500 can be an over-the-counter hearing aid, an in-the-earhearing, or any other style of hearing device. According to anembodiment, electronics, housing and battery 510 of audio device 500 canbe worn behind the ear. According to an embodiment, acoustic horn 520can be oriented to preferentially receive and amplify sound 530 arrivingfrom the front of the user. Benefits such as selective directionality,amplification, reduction in equivalent microphone self-noise, increasedmechanical support, feedback reduction resulting from the extendedacoustic path and phase shift between microphone and receiver, and/orincreased energy efficiency of the audio system can result from theconfiguration of audio system 500. According to an embodiment, areceiver or sound tube 540 can deliver sound 550 to the ear canal of theuser (not shown). According to an embodiment, acoustic horn 520 can forma curved ear hook and can be positioned over the top of the user's pinna(not shown). According to another embodiment, a portion of the acoustichorn 520 and a MEMS microphone can be enclosed within the hearing aidhousing 510. Those skilled in the art will recognize that there are amultitude of audio devices 500 which may benefit from a MEMS microphonewith acoustic horn, for example, hearing aids, over-the-counter hearingaids, hearables, wearables, personal sound amplifiers, televisions,radios, cell phones, telephones, computers, laptops, tablets, vehicleinfotainment systems, audio processing equipment and devices, personalmedia players, portable media players, audio reception systems,receivers, public address systems, media delivery systems, internetmedia players, smart speakers and devices, voice controlled systems,voice activated systems, recording devices, acoustic surveillance tools,built-in microphone systems, MEMS microphones, audio devices, subsystemswithin any of the above devices or systems, or any other device orsystem which processes audio signals.

FIG. 6 illustrates a schematic diagram of an audio system 600 comprisinga MEMS microphone 610 and a plurality of acoustic horns 620 and 622.According to an embodiment, audio system 600 can include additionalacoustic horns and/or MEMS microphones. MEMS microphone 610 may be anytype of MEMS microphone, for example, MEMS microphone 610 may be MEMSmicrophone die, a substrate of a MEMS microphone, a circuit board towhich a MEMS microphone is mounted, a top port MEMS microphone, a bottomport MEMS microphone, a side port MEMS microphone, a MEMS microphonewith digital output, or a MEMS microphone with analog output. Acoustichorn 620 and acoustic horn 622 may be any type of acoustic horns, forexample, acoustic horn 620 and acoustic horn 622 may be exponentialhorns, parabolic horns, conical horns, hyperbolic horns,hyperbolic-exponential or hypex horns, tractrix horns, flaring horns,horns with smooth continuous surfaces, or horns with discontinuous orstepped surfaces. Acoustic horn 620 and acoustic horn 622 can act asacoustic transformers, changing low pressure and high volume at themouths 640 and 642 of the horns 620 and 622 to high pressure and lowvolume at the throats 630 and 632 of the horns 620 and 622. Thecross-sectional area 650 of the horn 620 can be designed to increase asalong the axis 660 as the distance from throat 630 increases. Thecross-sectional area 652 of the horn 622 can be designed to increasealong the axis 662 as the distance from the throat 632 increases. Thecross-sectional areas 650 and 652 of the horns 620 and 622 at any pointalong axes 660 and 662 may be of any shape, for example, thecross-sectional areas may be circular, oval, rectangular, square,multi-sided, or combinations of these. Multiple acoustic horns, forexample, acoustic horn 620 and acoustic horn 622, may be configured andoriented to provide directional preference in any direction includingorientation to provide directional preference in the same direction oropposite directions. Multiple acoustic horns, for example, acoustic horn620 and acoustic horn 622, can have different total effective lengths;can be designed for different cut-off frequencies; can have differentmouth cross-sectional areas 640 and 642, and can have different throatcross-sectional areas 630 and 632.

FIG. 7 illustrates a cross-sectional view of an audio system 700. Audiosystem 700 comprises a MEMS microphone substrate 710; a MEMS microphoneenclosure or housing 720, a MEMS microphone Application SpecificIntegrated Circuit (ASIC) 730; a MEMS microphone diaphragm supportstructure 740; a MEMS microphone pressure-sensitive diaphragm 750; andan acoustic horn 770. A port opening 716 allows sound 790 to act uponthe MEMS microphone pressure-sensitive diaphragm 750. Electrical signals760 are communicated between the MEMS microphone pressure-sensitivediaphragm 750 and the MEMS ASIC 730. Sound 790 pressure acts against theMEMS microphone pressure-sensitive diaphragm 750 and an air cavity 792formed within the MEMS microphone device. Acoustic horn 770 has a throat772 with an internal cross-sectional area. Acoustic horn 770 has a mouth774 with an internal cross-sectional area. The cross-sectional area atthe mouth 774 is greater than the cross-sectional area at the throat.The cross-sectional area of horn 770 may change as a function of theeffective length 776 of the horn. The cross-sectional area may change ina step-wise fashion including one or more steps between throat 772 andmouth 774. According to an embodiment a plurality of steps can havevarying internal cross-sectional areas 778, 780, 782, 784 and 786. TheMEMS microphone substrate 710 has an inside surface 712 and an outsidesurface 714. The acoustic horn 770 is shown coupled to the outsidesurface 714 of the MEMS microphone substrate 710. According to anembodiment, the acoustic horn 770 and the MEMS microphone substrate 710can form a single integral element. According to another embodiment,acoustic horn 770 can be attached to outside surface 714 of MEMSmicrophone substrate 710 using one or more of various differentintermediaries, as described in relation to FIG. 3. According to anembodiment, there may be a multiplicity of stepped cross-sectional areassimilar to 778, 780, 782, 784, 786, and 774. According to an embodimentacoustic horn 770 can be printed with an additive manufacturingtechnology such as a three-dimensional (3D) printer.

FIG. 8 illustrates a cross-sectional view of an audio system 800. Audiosystem 800 comprises a MEMS microphone 810; a Printed Circuit Board(PCB) 820, an acoustic horn 830; attachment mechanism 840 to attach thePCB 820 to the acoustic horn 830; and an air-conduction sound path 850for air-conduction sound to travel through the acoustic horn 830 to theMEMS microphone 810. Sectional lines indicate that only portions of PCB820, acoustic horn 830, attachment mechanism 840, and air-conductionsound path 850 are shown in FIG. 8. MEMS microphone 810 comprises a MEMSmicrophone substrate 812, a MEMS microphone enclosure 811, a MEMSmicrophone Application Specific Integrated Circuit (ASIC) 813, a MEMSmicrophone diaphragm support structure 816, a MEMS microphonepressure-sensitive diaphragm 815, a wire or electrical connection 814between an output of pressure-sensitive diaphragm 815 and an input ofASIC 81, and a port opening 817 to allow air-conduction sound to actupon the pressure-sensitive diaphragm 815. According to an embodiment,MEMS microphone 810 can be a surface mount device. According to anembodiment, MEMS microphone 810 can be a bottom port device. Accordingto an embodiment, a conformal coating 860 can be used to seal MEMSmicrophone 810 to PCB 820. According to an embodiment, a 1 millimeter(mm) diameter through-hole 822 can be placed coaxial or near coaxialwith respect to port opening 817. According to an embodiment, a 1 mmhole 842 in attachment mechanism 840 can be placed coaxial or nearcoaxial with respect to through-hole 822. According to an embodiment,attachment mechanism 840 can comprise a double-sided mounting tape.According to other embodiments, attachment mechanism 840 can comprise agasket, a diaphragm, a moisture barrier, a flexible tube, anintermediate structure, a buffer material, a film, a layer, a sealant,an adhesive, glue, or epoxy, etc. According to an embodiment,air-conduction sound path 850 is effectively trapped between the surface852 of attachment mechanism 840 and surfaces 854 of acoustic horn 830.According to an embodiment, air-conduction sound path 850 can expandlinearly, or non-linearly, with the expanding surfaces 854 along theeffective length of an acoustic horn 830.

FIG. 9 illustrates a perspective view of an acoustic horn 900. Accordingto an embodiment, the size of acoustic horn 900 is 50 mm by 13 mm by 4mm. According to an embodiment, acoustic horn 900 can be constructedfrom plastic 910. Acoustic horn 900 has a top surface 920 that issubstantially flat. According to an embodiment, a double-sided mountingtape (not shown) can be used to attach the top surface 920 of acoustichorn 900 to the bottom side of a PCB (not shown) according to thedescription of FIG. 8. The mounting tape can have a hole or opening atleast over the mouth opening 930 of horn 900. Sound waves can enter horn900 via a mouth 940 and travel along a continuous channel or interiorstructure 950 of horn 900 and exit at throat 930. According to anembodiment, feature 930 can have about a 1 mm diameter hole which isabout 1 mm deep into top surface 920. Throat 930 can be coaxial with asurface mount MEMS microphone bottom port (not shown) positioned on aPCB (also not shown). According to an embodiment, continuous channel 950within the top surface 920 extends between throat 930 and mouth 940.According to an embodiment, channel 950, beginning at feature 930, canbe 1 mm wide by 1 mm deep and defines a throat cross-sectional area of 1mm² of acoustic horn 900. According to an embodiment, continuous channel950 deepens and widens such as indicated at channel locations 960 and970. The widening and deepening of continuous channel 950 can occurgradually or in a step-wise fashion. Channel 950 terminates at mouth940. Mouth 940 is exposed to air-conduction sound in the horn'senvironment. According to an embodiment, the cross-sectional area of themouth can be about 7.4 mm by about 3 mm (22.2 mm²) and the effectivelength of channel 950 can be about 186.8 mm, which corresponds to asound wavelength at about 1836 Hz at 20 degrees Celsius. Accordingly, aneffective length of channel 950 of 186.8 mm will tend to amplify speechfrequencies above 459 Hz, corresponding to the cutoff frequency ofacoustic horn 900. Efficient amplification for acoustic horn 900 canbegin at about least ½ octave above the cutoff frequency or about 688Hz. Speech frequencies above about 688 Hz can be difficult to hear bymany hearing impaired individuals. According to an embodiment, anacoustic horn 900 with a throat cross-sectional area of 1 mm² and amouth cross-sectional area of 22.2 mm² can provide as much as 13.4 dB ofamplification. Furthermore, maximum amplification will occur for soundsources within a 20 degree window perpendicular to mouth 940. Thedimensions and parameters of acoustic horn 900 can be designed to matchthe footprint portion of a component of an audio system, such as abattery housing. According to an embodiment the footprint of acoustichorn 900 can be designed to match the size of a KEYSTONE 2466 “AAA”battery holder, and acoustic horn can be physically sandwiched between aKEYSTONE 2466 battery holder and a PCB having a double-sided mountingtape in contact with acoustic horn 900. One skilled in the art willrecognize that any mating, flat surface, component similar to a PCB mayalso be combined or attached to top surface 920 in order to enclosechannel 950 for purposes of enabling acoustic horn 900. Acoustic horn900 can comprise, as described, an assembly of multiple components oralternatively, acoustic horn 900 can comprise a single, integral piece.According to an embodiment, acoustic horn 900 can be manufactured usinginjection molding or additive manufacturing technologies for purposes ofcreating one or more components which when assembled form acoustic horn900.

According to an embodiment, an audio system similar to any of the audiosystems described above in reference to FIGS. 1-9 can further includeone or more additional MEMS microphone or other type of microphones. Theadditional microphones may or may not be coupled to an acoustic horn.Signal analysis and processing techniques can be applied to the signalsgenerated comparatively by each microphone (whether horned orun-horned). Such techniques can yield information about the acousticenvironment of a user of an audio system and can derive content andparameters from such acoustic environment of the user which can beuseful in increasing the speech intelligibility of a processed audiosignal that can be presented to a user of an audio system.

In reference to all of the foregoing disclosure, the above describedembodiments enable solutions, improvements, and benefits to manyproblems and issues affecting conventional audio systems andconventional audio devices and offer improved functionality for audiosystems and audio devices, for example:

First, utilizing the very small port size or die size of MEMSmicrophones, horns provide mechanical amplification prior to MEMSmicrophone acoustic signal reception.

Second, recognizing the high frequency content for intelligible speech,the effective length requirements for horns are reduced.

Third, the use of mechanical amplification with horns prior to MEMSmicrophone acoustic signal reception increases the signal-to-noise ratioof the MEMS microphones making at-a-distance acoustic signal receptionmore tolerable for the user.

Fourth, using the directional preference of the horn provides MEMSmicrophones with a unidirectional response for acoustic signaldiscrimination which can be especially beneficial in otherwise noisyenvironments such as automobiles, crowds, restaurants, and classrooms.

Fifth, combining an acoustic horn with a MEMS microphone provides a lowcost solution for increased at-a-distance speech intelligibility.

Sixth, combining an acoustic horn with a MEMS microphone enablesapplications requiring small physical size such as hearables and hearingaids.

Seventh, an acoustic horn can provide additional physical support forplacing an audio system or hearing aid in contact with a user.

Eighth, an acoustic horn can decrease the energy consumption of an audiosystem thereby increasing its energy efficiency.

Ninth, the signal generated by a first horned microphone can becompared, analyzed, or processed with respect to a signal generated by asecond horned microphone. Differences between the respective signals dueto differences in the physical characteristics of each horn and/or intheir direction can be exploited to generate information useful forprocessing the audio signal(s) and increasing the speech intelligibilityof the processed signal to a user.

Tenth, the signal generated by a first horned microphone can becompared, analyzed, or processed with respect to a signal generated by asecond un-horned microphone. Differences between the respective signalsdue to the differences in one microphone being horned and the othermicrophone being un-horned can be exploited to generate informationuseful for processing the audio signal(s) and increasing the speechintelligibility of the processed signal to a user.

Eleventh, for applications requiring small physical size such ashearables and hearing aids, the horn extends the acoustic path and phasedifference between the MEMS microphone and the receiver greatlydiminishing potential feedback. For most users, a non-occluding,open-fit configuration is preferable especially if other objects can beused in immediate proximity, such as a cell phone.

In view of the above it is evident that acoustic horns for MEMSmicrophones have at least the following characteristics: low cost, smallsize, improved signal-to-noise, improved at-a-distance speechintelligibility, directional discrimination, reduced feedback, andincreased energy efficiency of audio systems.

Benefits, other advantages, and solutions to problems and issues havebeen described above with regard to particular embodiments. Any benefit,advantage, solution to problem, or any element that may cause anyparticular benefit, advantage, or solution to occur or to become morepronounced are not to be construed as critical, required, or essentialfeatures or components of any or all the claims.

In view of all of the above, it is evident that novel audio systems,audio devices, microphones, and methods are disclosed.

While the subject matter of the invention is described with specific andexample embodiments, the foregoing drawings and descriptions thereofdepict only typical embodiments of the subject matter, and are nottherefore to be considered limiting of its scope. It is evident thatmany alternatives and variations will be apparent to those skilled inthe art and that those alternatives and variations are intended to beincluded within the scope of the present invention. For example, someembodiments described herein include some elements or features but notother elements or features included in other embodiments, thus,combinations of features or elements of different embodiments are meantto be within the scope of the invention and are meant to form differentembodiments as would be understood by those skilled in the art.Furthermore, any of the above-described elements, components, blocks,systems, structures, devices, ranges and selection of ranges,applications, programming, signal processing, signal analysis, signalfiltering, implementations, proportions, flows, or arrangements, used inthe practice of the present invention, including those not specificallyrecited, may be varied or otherwise particularly adapted to specificenvironments, users, groups of users, populations, manufacturingspecifications, design parameters, or other operating requirementswithout departing from the scope of the present invention. Additionally,the steps recited in any method or processing scheme described above orin the claims may be executed in any order and are not limited to thespecific order presented in the above description or in the claims.Finally, the components and/or elements recited in any apparatus claimsmay be assembled or otherwise operationally configured in a variety ofpermutations and are accordingly not limited to the specificconfiguration recited in the claims.

As the claims hereinafter reflect, inventive aspects may lie in lessthan all features of a single foregoing disclosed embodiment. Thus, thehereinafter expressed claims are hereby expressly incorporated into thisDetailed Description of the Drawings, with each claim standing on itsown as a separate embodiment of the invention.

What is claimed is:
 1. A hearing aid, comprising: a MEMS microphonepackage, wherein the MEMS microphone package comprises a substratehaving a first surface and a second surface opposite the first surface,and wherein the substrate also comprises a port hole extending throughthe substrate from the first surface to the second surface; a MEMSmicrophone within the MEMS microphone package; an acoustic horn having athroat opening, a mouth opening, an inner surface, and an outer surface,wherein the throat opening is attached to the second surface of thesubstrate and encloses the port hole, and wherein the inner surface ofthe acoustic horn defines a cross-sectional area that increases alongthe length of the acoustic horn from the throat opening to the mouthopening.
 2. The hearing aid of claim 1, wherein a ratio of an innercross-sectional area at the mouth opening to an inner cross-sectionalarea at the throat opening is between 4:1 and 25:1.
 3. The hearing aidof claim 1, wherein the acoustic horn has an effective length between 40mm and 250 mm.
 4. The hearing aid of claim 1, wherein a portion of anacoustic channel extending from the throat opening of the acoustic hornto the mouth opening of the acoustic horn, extends substantiallyperpendicular to the second surface of the substrate.
 5. The hearing aidof claim 4, wherein a portion of the acoustic channel includes at leastone bend.
 6. The hearing aid of claim 1, wherein the acoustic horn isoriented to preferentially receive sound arriving from the front of auser of the hearing aid.
 7. The hearing aid of claim 6, furthercomprising a second MEMS microphone and a second acoustic horn coupledto the second MEMS microphone, wherein the acoustic horn and the secondacoustic horn are configured to point in different directions.
 8. Thehearing aid of claim 1, wherein the cross-sectional area that increasesalong the length of the acoustic horn from the throat opening to themouth opening, increases in a stepped manner along the length of atleast a portion of the acoustic horn.
 9. The hearing aid of claim 1,wherein the acoustic horn forms an ear hook configured to position ahearing aid relative to an ear of a user of the hearing aid.
 10. Thehearing aid of claim 1, wherein the acoustic horn comprises an interiormaterial configured to facilitate acoustic amplification and an outermaterial configured to facilitate acoustic attenuation.
 11. The hearingaid of claim 10, wherein the interior material comprises a rigidmaterial and wherein the exterior material comprises less rigidmaterial.
 12. The hearing aid of claim 1, wherein the acoustic horn isintegral with the substrate forming a monolithic structure.
 13. Thehearing aid of claim 1, wherein the acoustic horn is configured tosubstantially amplify sound frequencies within the audible frequencies.14. The hearing aid of claim 1, wherein the acoustic horn is configuredto substantially amplify sound frequencies above 1000 Hz and within theaudible frequencies.
 15. An audio system, comprising: a MEMS microphonepackage, wherein the MEMS microphone package comprises a substratehaving a first surface and a second surface opposite the first surface,and wherein the substrate also comprises a port hole extending throughthe substrate from the first surface to the second surface; a MEMSmicrophone within the MEMS microphone package; an acoustic horn coupledto the second surface of the substrate, wherein the acoustic horncomprises a throat opening, a mouth opening, and an acoustic channelextending between the mouth opening and the throat opening, and whereinthe second surface of the substrate overlays the acoustic channel fromthe mouth opening to the throat opening.
 16. The audio system of claim15, wherein the acoustic channel has a cross-sectional area thatincreases along the length of the acoustic channel from the throatopening to the mouth opening.
 17. The audio system of claim 16, whereina depth of the acoustic channel as measured from the second surface ofthe substrate to a base surface of the acoustic channel increases alongthe length of the acoustic channel from the throat opening to the mouthopening.
 18. The audio system of claim 16, wherein a width of theacoustic channel increases along the length of the acoustic channel fromthe throat opening to the mouth opening.
 19. An audio system,comprising: a plurality of MEMS microphones; a plurality of acoustichorns coupled to the MEMS microphones, wherein each of the plurality ofacoustic horns is pointed in a different direction.
 20. The audio systemof claim 19, wherein the audio system comprises a voice-controlled smartspeaker.